As I understand it, this is a key-in-knob type retrofit cylinder, intended for instant core swaps like a standard IC (though operating on a different principle). What you have appears to be the core only, not the false bible housing.
With a standard key, the cylinder operates like any other. To remove, a control key with elongated bitting and blade is used to turn the plug to about ten o'clock. Once oriented, the key is pushed farther in (hence the elongated bitting), which disengages the retaining pin and allows core removal.
The spring-loaded projection on the key, as I understand it, "unlocks" the plug for rotation. See US Patent 4,823,575 for more detail (as well as a detailed, exploded view of a cylinder like this.
http://www.google.com/patents/US4823575Take this with a grain of salt; I've never used one of these, only read up on them.